Voice over Internet Protocol (“IP”) (“VoIP”) provides for new possibilities in the provision of telephone and collaborative services to homes, small businesses and large enterprises. Formerly, cost was a major factor in the selection of these services. Homes and many small businesses could not afford to purchase advanced private branch exchange (“PBX”) capabilities despite the many benefits that this could supply to them. The same could be said about branch office locations for large enterprises. It was difficult to justify PBX services due to the small numbers of employees over which the cost could be amortized.
VoIP that typically employs sophisticated processor based telephone sets, offers new possibilities for reducing telephone system cost. Such systems can be widely distributed linked by a data network and the desirable features of a PBX can be provided over the WAN from a remote location. A local dedicated controller is no longer required for small branch offices. Similarly a hosted PBX service can be provided to small business by specialist service providers.
Increasingly, VoIP networks with PBX-level services will be set up in homes, small business and large enterprise branch office locations. However, it is not economic or practical in these circumstances to expect that specialist personnel will be available to configure these networks, or for specialized equipment to be located at these locations. In a similar way, it is unrealistic to expect that trained specialists will be available to manage the operations of these networks. Home and small business systems will often be obtaining service from a network service provider. A service provider will be supplying service to thousands or tens of thousands of small businesses and to perhaps millions of home networks. In the case of a large enterprise, supplying of information technology (“IT”) support to large numbers of branch offices, while more feasible than the service provider example, is still an expense that the enterprise would rather do without.
For example, one problem with such VoIP networks is that each device on such networks is independent and substantially functionally identical when it comes to the operation of VoIP services. Yet, such devices all share the resources of an internal local area network (“LAN”) and a shared link to a wide area network (“WAN”) such as the Internet. It is over these shared links that all calls to devices not on the LAN will be set up. Typically, the bandwidth on the external link will be limited. In typical networks, it will not be possible for all devices to have an outgoing call set up at the same time. This leads to a difficulty in that there are situations in which calls could fail or experience poor quality of service because too many calls are simultaneously trying to share the common limited pool of bandwidth.
There are prior art approaches to such problems. One approach is to integrate the devices into a larger application. This is the sort of resource management that is done by a PBX. The PBX provides an environment in which devices such as telephones and external connection resources such as trunks (IP or otherwise) are controlled by an integrated software system. Resource Manager software elements are often provided that contain policies on the allocation of resources. Since the PBX has visibility of all calls, bandwidth can be managed by disallowing calls which would exceed capacity. Similarly, access to and use of other shared resources in the system can also be managed centrally.
Another approach is to provide intelligence in the resource. The resource itself would be able to allocate access to itself based on the relative priorities of the requests. This could be done with a resource which has intrinsic intelligence. However a dumb or legacy resource can be wrapped with elements such as proxies, mediators, etc., that can provide this intelligence. One example of intelligence in the resource is use of the Internet Engineering Task Force (“IETF”) Resource ReSerVation Protocol (“RSVP”). This can allow end devices such as IP Phones to negotiate bandwidth resources directly with the network infrastructure, for example using Resource Reservation Protocol (RSVP as described in Braden et al., Resource ReSerVation Protocol (RSVP)—Version 1 Functional Specification Network Working Group, IETF Request for Comments 2205. However these techniques can add considerable complexity to deployment, and require RSVP-aware network elements be in place across all parts of the network where call media would potentially flow. The latter assumption can add large complexity and/or costs and may not be feasible in the general case of arbitrary pairs of endpoints involved in the flows, which is extremely common, if not fundamental, to VoIP applications.
Yet in certain configurations, no higher level application such as a PBX can assumed. Having such a higher level application would defeat the economies that are an advantage of highly distributed VoIP systems. For the wrapper or proxy alternative, no server is available on which to carry this service—devices are functionally identical with respect to their control of bandwidth and the lower level bandwidth resource has no capacity to supply this service. Wrapper and proxy functions generally do not involve themselves in call details, has no visibility of available bandwidth or other resources, and may not have knowledge of all calls or other resource consumption in progress.